Many thanks to Pamela Hansen who just tipped me off to this source for CUSTOM Cradled wooden frames. I haven't used them, but it is worth checking out if you are having a hard time locating a cabinet maker in your area to make custom wooden cradled panels for you. Here is what she wrote to me 11.17.2020:
"I did finally find a website rexart.com that sells conventional sizes with quite a large selection in sizes for good prices. But you can also order custom sizes. They are a bit pricy for that so before you place that order, check to see if they already offer that size. Also free shipping over $100. "
Thank you, Pamela Hansen!!